Editing Microphone (section)

===Cardioid, hypercardioid, supercardioid, subcardioid <span class="anchor" id="Cardioid"></span>===
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[[File:Us664a microphone.jpg|thumb|University Sound US664A dynamic supercardioid microphone]]

The most common unidirectional microphone is a '''cardioid''' microphone, so named because the sensitivity pattern is "heart-shaped" (i.e. a [[cardioid]]). The cardioid family of microphones are commonly used as vocal or speech microphones since they are good at rejecting sounds from other directions. In three dimensions, the cardioid is shaped like an apple centered around the microphone, which is the "stem" of the apple. The cardioid response reduces pickup from the side and rear, helping to avoid feedback from the [[Foldback (sound engineering)|monitors]]. Since these directional transducer microphones achieve their patterns by sensing pressure gradient, putting them very close to the sound source (at distances of a few centimeters) results in a bass boost due to the increased gradient. This is known as the [[Proximity effect (audio)|proximity effect]].<ref>[http://www.tonmeister.ca/main/textbook/node473.html Proximity Effect.] {{Webarchive|url=https://web.archive.org/web/20071016054151/http://www.tonmeister.ca/main/textbook/node473.html |date=October 16, 2007 }} Geoff Martin, ''Introduction to Sound Recording''.</ref> The SM58 has been the most commonly used microphone for live vocals for more than 50 years<ref>{{cite web |url=http://www.shure.com/americas/about-shure/history/index.htm |title=History – The evolution of an audio revolution |publisher=Shure |access-date=July 30, 2013 |archive-date=July 16, 2012 |archive-url=https://web.archive.org/web/20120716182548/http://www.shure.com/americas/about-shure/history/index.htm }}</ref> demonstrating the importance and popularity of cardioid mics.

The cardioid is effectively a superposition of an omnidirectional (pressure) and a figure-8 (pressure gradient) microphone;<ref>{{Cite book |url=https://books.google.com/books?id=KApvYcQkY_gC |title=Eargle's The Microphone Book: From Mono to Stereo to Surround – A Guide to Microphone Design and Application |last=Rayburn |first=Ray A. |date=November 12, 2012 |publisher=Taylor & Francis |isbn=9781136118135 }}</ref> for sound waves coming from the back, the negative signal from the figure-8 cancels the positive signal from the omnidirectional element, whereas, for sound waves coming from the front, the two add to each other. However, in low frequencies a cardioid microphone behaves as an omnidirectional microphone.

By combining the two components in different ratios, any pattern between omni and figure-8 can be achieved, which comprise the first-order cardioid family.  Common shapes include:
* A '''hyper-cardioid''' microphone is similar to cardioid, but with a slightly larger figure-8 contribution, leading to a tighter area of front sensitivity and a smaller lobe of rear sensitivity.  It is produced by combining the two components in a 3:1 ratio, producing nulls at 109.5°.  This ratio maximizes the [[directivity factor]] (or directivity index).<ref name=":0">{{Cite journal |title= On the Design and Implementation of Higher Order Differential Microphones|issue=1 |pages=162–174 |journal=IEEE Transactions on Audio, Speech, and Language Processing |volume=20 |doi=10.1109/TASL.2011.2159204 |date=January 2012 |last1=Sena |first1=E. De |last2=Hacihabiboglu |first2=H. |last3=Cvetkovic |first3=Z. |s2cid=206602089 }}</ref><ref name=":1">{{Cite book |url=https://books.google.com/books?id=tym4kKVPfaAC |title=Study and Design of Differential Microphone Arrays |last1=Benesty |first1=Jacob |last2=Jingdong |first2=Chen |date=October 23, 2012 |publisher=Springer Science & Business Media |isbn=9783642337529 }}</ref>
* A '''super-cardioid''' microphone is similar to a hyper-cardioid, except there is more front pickup and less rear pickup.  It is produced with about a 5:3 ratio, with nulls at 126.9°.  This ratio maximizes the ''front-back ratio''; the energy ratio between front and rear radiation.<ref name=":0" /><ref name=":1" />
* The '''sub-cardioid''' microphone has no null points. It is produced with about 7:3 ratio with 3–10&nbsp;dB level between the front and back pickup.<ref>{{cite web|url=http://www.uaudio.com/webzine/2005/december/text/content2.html |title=Ask the Doctors: The Physics of Mid-Side (MS) Miking |first=Dave |last=Berners |publisher=Universal Audio |work=Universal Audio WebZine |date=December 2005 |access-date=July 30, 2013}}</ref><ref>{{cite web |url=http://hyperphysics.phy-astr.gsu.edu/hbase/audio/mic3.html#c2 |title=Directional Patterns of Microphones |access-date=July 30, 2013 }}</ref>
Three such cardioid microphones/hydrophones could be orthogonally oriented as a collocated triad to improve the gain and also create a steerable beam pattern.<ref name="WongKT0218">{{cite journal |last1=Wong |first1=Kainam |last2=Nnonyelu |first2=Chibuzo |last3=Wu |first3=Yue |title=A Triad of Cardioid Sensors in Orthogonal Orientation and Spatial Collocation – Its Spatial-Matched-Filter-Type Beam-Pattern |journal=IEEE Transactions on Signal Processing |date=February 2018 |volume=66 |issue=4 |pages=895–906 |doi=10.1109/TSP.2017.2773419 |bibcode=2018ITSP...66..895W |s2cid=3298960 |url=https://ieeexplore.ieee.org/document/8106745 |access-date=February 1, 2021}}</ref><ref>{{cite journal |last1=Nnonyelu |first1=Chibuzo |last2=Wong |first2=Kainam |last3=Wu |first3=Yue |title=Cardioid microphones/hydrophones in a collocated and orthogonal triad—A steerable beamformer with no beam-pointing error |journal=The Journal of the Acoustical Society of America |date=January 2019 |volume=145 |issue=1 |pages=575–588 |doi=10.1121/1.5087697 |pmid=30710946 |bibcode=2019ASAJ..145..575N |s2cid=73422758 |url=https://asa.scitation.org/doi/abs/10.1121/1.5087697 |access-date=February 1, 2021 }}</ref>